Fix 'process launch -i' for remote processes

We want to forward stdin when stdio is not disabled and when we're not
redirecting stdin from a file.

renamed m_stdio_disable to m_stdin_forward and inverted value because
that's what we want to remember.

There was previously a bug that if you redirected stdin from a file,
stdout and stderr would also be redirected to /dev/null

Adds support for remote target to TestProcessIO.py

Fixes ProcessIOTestCase.test_stdin_redirection_with_dwarf for remote
Linux targets

llvm-svn: 228744